Marine structures not only consist of sheet pile walls, but also isolated partially submerged hollow or solid structures for example marine structures such as piers, wharfs, drilling platforms, columns, pipes and piles, pilasters, stanchions, pylons legs, piling, and uprights and any other supporting member. The supporting members may be comprised of wood, concrete, metal beams and the like. Such partially submerged structures whether isolated or not require treatment to prevent and/or combat corrosion by salt water and/or water-borne pollution in seawater, brackish water or freshwater as well as infestation by marine organisms such as barnacles in salt water and zebra mussels in freshwater.
In order to perform maintenance or control operations on these partially submerged hollow or solid structures for example to check the level of corrosion, perform treatment against corrosion or replace or repair corroded parts of the structures, it is useful to make these structures easily accessible in a dry environment. Dry setting installations, also referred to as cofferdams or caissons, enable free access to the site in a dry environment.
U.S. Pat. No. 5,292,206 discloses a device for sealing a caisson comprising a bottom, two upright side walls and a back wall in a watertight way against a sheet pile wall having a longitudinal profile composed of a succession of grooves and ridges, said device comprising the combination of: a) an inflatable continuous air chamber extending along the bottom of the caisson over the total width of the caisson and along the upright side walls thereof to sealingly engage the ridges of the sheet pile wall while conforming to irregularities therein; b) a series of deformable sealing elements disposed along the bottom of the caisson to sealingly engage the grooves of the sheet pile wall, each having a profile approaching the profile of a groove, which elements are each mounted between two horizontal guiding plates disposed one above the other in a manner such as to allow a displacement of the elements in the direction of the sheet pile wall in front of the grooves therein, while said inflatable air chamber is provided for pressing these elements against the wall to enable the deformable sealing elements to adapt to deformed and irregular grooves; c) a core provided between each of said sealing elements and the air chamber, which core is adapted to be displaced between said guiding plates and is fixed to the adjoining sealing element; and d) means for allowing a lateral displacement of said sealing elements together with the guiding plates above and underneath these sealing elements with respect to the caisson.
EP 2163692A discloses a dry setting installation (1) for generating a substantially dry working space for carrying out work at an underwater structure, the dry setting installation (1) comprising two side-walls (2), a back wall (3), a bottom (4) and, for each side-wall, a side edge sealing means (20) provided on the side-wall edge for providing a substantially sealing contact between the side-walls (2) and the underwater structure, characterised in that the dry setting installation comprises a distance variation means (30) for varying the distance between the side edge sealing means (20) of the two side-walls (2).
GB 2114636A discloses a working chamber for use in underwater work on an underwater member, the chamber consisting of two or more chamber sections which can be locked together in contact with each other; an opening being provided at the bottom and the top of the chamber and adapted for the introduction of the member in connection with which the chamber is to be used; a sealable manhole being provided in the upper part of the chamber.
GB 2226843A discloses an apparatus for allowing work to be carried out on a foundation pile, at least part of which is submerged, comprising means for locating a work platform around the pile, the work platform being surrounded by an upwardly extending wall, means for providing a seal between the work platform and the pile, means for locating the work platform in a desired location relative to the pile whilst the seal between the work platform and the pile is being effected and means for removing any water between the surrounding wall and the pile from above the seal. In a preferred embodiment the work platform is formed in two portions, each portion of the work platform having a part-circular cut-out and a section of wall secured thereto.
GB 2046818A discloses equipment for carrying out underwater operations on the exposed head sections of foundation piles and the like, the equipment having a submergible water-free working chamber adapted to be disposed over the exposed head section, a floor near the bottom edge of the chamber, the floor having an aperture with sealing means for sealing between the head section of a foundation pile requiring attention and the floor, and the working chamber being connected to at least one shaft extending upwardly for projection beyond the water surface.
U.S. Pat. No. 5,324,140 discloses a flexible, submersible compartment which allows a user to perform repairs on submerged structures in dry conditions in the presence of rigid obstacles, said compartment comprising: a flexible diving bell adapted to be inflated so as to partially enclose a submerged structure, said flexible diving bell having an opening at an upper portion; a collar attached to said flexible bell at the opening including a seal element for sealing the opening about the submerged structure; and a lower platform-brace attached to said flexible bell comprising a plurality of interconnected modules for anchoring to the structural element, each module including a boundary member wherein the boundary members of the interconnected modules form a discontinuous ring, at least two of the modules including a boundary member having first and second pivotally interconnected segments; whereby said flexible bell when inflated, and the second segments contract upon contact with a rigid obstacle.
A major problem with maintenance of any kind is the hinder that it engenders. This is particular serious in the case of hinder to waterways and marine installations e.g. harbours, ports, bridges and oil platforms. It is important that such hinder should be reduced to a minimum. There is a therefore a need for rapidly mountable and demountable installations allowing such work to be carried out expeditiously. A further requirement is that the installation be as compact as possible both as regards limiting physical hinder during the maintenance activities and providing accessibility to isolated partially submerged structures very close to one another.
The cited prior art provides solutions to the problem of inspecting and/or repairing and/or maintaining an isolated structure by surrounding it by an installation. However, many structures are not isolated and even if isolated may not be fully surroundable with an installation.